There is a growing need for expanded telephone communication capabilities within the home. This need is driven by two major factors: the increasing use of additional outside lines and the desirability of exchange functionality within the home, such as for intercom systems.
Telephone Wiring
An in-home telephone service usually employs two or four wires, and is accessed via telephone outlets into which the telephone sets are connected. FIG. 1 shows the wiring configuration of a prior-art telephone system 10 for a residence or other building, wired with a residential telephone line 5. The residential telephone line 5 consists of single wire pair which connects to a junction-box 16, which in turn connects to a Public Switched Telephone Network (PSTN) 18 via a cable 17a, terminating in a public switch 19, which establishes and enables telephony from one telephone to another. The term “analog telephony” as used herein denotes traditional analog low-frequency audio voice signals typically under 3 KHz, sometimes referred to as “POTS” (“Plain Old Telephone Service”), whereas the term “telephony” in general denotes any kind of telephone service, including digital service such as Integrated Services Digital Network (ISDN). The term “high-frequency” as used herein denotes any frequency substantially above such analog telephony audio frequencies, such as that used for data. ISDN typically uses frequencies not exceeding 100 KHz (typically the energy is concentrated around 40 KHz). The term “telephone line” as used herein denotes electrically-conducting lines which are intended primarily for the carrying and distribution of analog telephony, and includes, but is not limited to, such electrically-conducting lines which may be pre-existing within a building and which may currently provide analog telephony service. The term “telephone device” as used herein denotes, without limitation, any apparatus for telephony (including both analog telephony and ISDN), as well as any device using telephony signals, such as fax, voice-modem, and so forth.
Junction box 16 is used to separate the in-home circuitry from the PSTN and is used as a test facility for troubleshooting as well as for wiring new in the home. A plurality of telephones 13a and 13b connects to telephone line 5 via a plurality of telephone outlets 11a, 11b, 11c, and 11d. Each outlet has a connector (often referred to as a “jack”), denoted in FIG. 1 as 12a, 12b, 12c, and 12d, respectively. In North America, RJ-11 is commonly used. Each outlet may be connected to a telephone unit via a connector (often referred to as a “plug”), denoted in FIG. 1 (for the two telephone units 13a and 13b illustrated) as 14a and 14b, respectively. It is also important to note that lines 5a, 5b, 5c, 5d, and 5e are electrically different segments of the same paired conductors.
While network 10 exhibits serial or daisy-chained topology wherein the wiring is serialized from an outlet to the next one only, other topologies such as star, tree or any arbitrary topology may also be used. The telephone wiring system within a residence, however, is always composed of wired media: two or four copper wires, and outlets which provide direct access for connecting to these wires.
Additional Subscriber Lines
FIG. 2 illustrates a telephone network 20 in a home, where an additional subscriber line 17b is required to be added to existing line 17a. Additional line 17b comes from exchange 18 to home junction-box 16. In order to provide access to additional line 17b, a new outlet 11e must be installed. In addition, a new telephone line 6a must be installed, routed from junction box 16 to the outlet 11e. In such an installation, a telephone set 13c is connected using a cable 15c, via connectors 14c and 12e to the added subscriber line.
Alternatively, the new wiring 6a can be routed together and as part of existing wiring 5, using the same in-wall routing. In such a case, either several new telephone outlets need to be installed, or the existing outlets need to be replaced with ones employing two or more telephone connectors.
In both the cases described above, new wiring must be added. The routing and installation of such wiring is both labor-intensive and expensive. Adding the new wiring on the exterior of the wall is less expensive, but may be aesthetically undesirable.
In buildings where four wires (two pairs) have been installed, adding a second subscriber line is quick and easy. The second pair of the existing wiring is used for the second subscriber line, thus obviating the need for routing additional wires. However, the same problem of needing additional wires is encountered in this case when a third or fourth subscriber line is required. In general, additional wiring is required whenever adding a new subscriber line to a home exceeds the capacity of the existing wiring.
FIG. 2 illustrates the case where the added subscriber lines involve the use of dedicated wiring from the exchange to the home for each such added subscriber line. New technology, however, enables multiple voice channels to be carried over a single twisted-pair (local-loop), Specifically, Digital Subscriber Line (DSL) technologies are available. For example, ISDN-BRA (Integrated Services Digital Network—Basic Rate Access, commonly referred to as ISDN) can carry two voice channels over a single twisted pair, HDSL (High Bit rate Digital Subscriber Line) supports up to 16 voice channels, and HDSL2 supports up to 30 voice channel over a single twisted pair. These and other such technologies commonly employ two modems, connected to each end of the twisted pair, as shown in network 30 in FIG. 3. The pair 17 in the local loop interfaces in the exchange side with an exchange terminal unit 32, which communicates over the local loop pair to a remote terminal unit 31, located at the customer side of the cable. Remote terminal unit 31 in turn provides subscriber line interfaces 17a and 17b, connected to junction box 16. In an alternate configuration, the voice channels are multiplexed within a digital stream, such as PCM highway, ATM or other buses.
The recent move towards de-regulation has enabled the subscriber to receive telephone services from providers other than the traditional telephone companies. One example is the competitive carriers in the United-States. In addition, non-telephone businesses, such as cable television and satellite-based network providers, are starting to offer telephone services. Thus, the customer may select added subscriber lines to be supplied by different service providers. FIG. 4 illustrates a configuration for such a customer, employing a telephone network 40. A first telephone line is supplied by a traditional telephone company as shown in FIG. 1 and previously described. However, a second telephone line is provided by a non-original telephone provider, which connects to non-telephone network 41. For example, this can be a cable television network. The voice channel is provided via a remote terminal unit 42, which provides the additional telephone line 6a, and communicates with the non-telephone network 41. For example, the remote terminal unit 42 can be part of Set-Top Box or Cable Modem.
Exchange Features
As used herein, the phrase “PABX-type features”, or the idiomatic equivalent thereof, is intended to encompass features including, but not limited to: hold/call pick up; call transfer between subsets; conference calls; calls coming from, or going to, a central office exchange; ringing on all subsets; repertory dialing; memory dialing. A rapid expansion in residential-oriented telephone systems and equipment has been developing to satisfy an ever growing number of needs related to telephone communication. One particular need in many residences is the ability to selectively communicate among a number of telephone sets all of which are connected via the single central office telephone line that accesses the residence. In addition, other identified needs of residential subscribers are similar to those of businesses having a private automatic branch exchange (PABX). However, most such existing exchanges require ‘star’ topology, in which all outlets are directly connected to the exchange. While this topology is supported in some residences, most buildings do not employ such a topology, as the example in FIG. 1 illustrates. In such a case, a private automatic branch exchange cannot easily be employed, unless effort is made to modify the wiring into ‘star’ topology. U.S. Pat. Nos. 4,821,319, 4,459,434, 5,090,052, 5,596,631, 5,781,622 and 6,038,300, as well as other patents classified under US Classes 379/177 and 379/363, disclose a few embodiments enabling limited exchange functionalities in a residence using single wire pair.
Data over Telephone Lines
There is a requirement for simultaneously using the existing telephone infrastructure for both telephone and data networking. In this way, the task of establishing a new local area network in a home or other building is simplified, because there would be no additional wires to install. U.S. Pat. No. 4,766,402 to Crane (hereinafter referred to as “Crane”) teaches a way to form a LAN over two-wire telephone lines, but without the telephone service.
The concept of frequency domain/division multiplexing (FDM) is well-known in the art, and provides means of splitting the bandwidth carried by a wire into a low-frequency band capable of carrying an analog telephony signal and a high-frequency band capable of carrying data communication or other signals. Such a mechanism is described, for example, in U.S. Pat. No. 4,785,448 to Reichert et al (hereinafter referred to as “Reichert”). Also widely used are xDSL systems, primarily Asymmetric Digital Subscriber Loop (ADSL) systems.
As another example, relevant prior-art in this field is disclosed in U.S. Pat. No. 5,896,443 to Dichter (hereinafter referred to as “Dichter”). Dichter suggests a method and apparatus for applying frequency domain/division multiplexing (FDM) technique for residential telephone wiring, enabling simultaneously carrying telephone and data communication signals. The bandwidth enabled by the wiring is split into a low-frequency band capable of carrying an analog telephony signal and a high-frequency band capable of carrying data communication signals. In such a mechanism, the telephone service is not affected, while data communication capability is provided over existing telephone wiring within a home.
The Dichter network is illustrated in FIG. 5, which shows a network 50 serving both telephones and providing a local area network of data units. Data Terminal Equipment (DTE) units 24a, 24b, and 24c are connected to the local area network via Data Communication Equipment (DCE) units 23a, 23b, and 23c, respectively. Examples of Data Communication Equipment include modems, line drivers, line receivers, and transceivers (the term “transceiver” as used herein denotes a combined transmitter and receiver). DCE units 23a, 23b, and 23c are respectively connected to high pass filters (HPF) 22a, 22b, and 22c. The HPF's allow the DCE units access to the high-frequency band carried by telephone-line 5. In a first embodiment (not shown in FIG. 5), telephones 13a, 13b, and 13c are directly connected to telephone line 5 via connectors 14a, 14b, and 14c, respectively. However, in order to avoid interference to the data network caused by the telephones, in a second embodiment (shown in FIG. 5) low pass filters (LPF's) 21a, 21b, and 21c are added to telephones 13a, 13b, and 13c from telephone line 5. Furthermore, a low pass filter may also be connected to Junction Box 16, in order to filter noises induced from or to the PSTN wiring 17. It is important to note that lines 5a, 5b, 5c, 5d, and 5e are electrically different segments of the same paired conductors.
Additional prior-art patents in this field can be found under US Class 379/093.08, which relates to carrying data over telephone wiring without any modifications made to the telephone wiring (e.g. wires and outlets), U.S. Pat. No. 5,841,360 and U.S. patent application Ser. Nos. 09/123,486 and 09/357,379 to the present inventor are the first to suggest modifying the telephone wiring, by means of splitting the wiring into distinct segments, each of which connects two telephone outlets. In this way, the network is modified from ‘bus’ topology into multiple ‘point-to-point’ segments, enabling superior communication characteristics.
Part of such a network 60 is shown in FIG. 6, describing outlets 31a and 31b, substituting outlets 11 of FIG. 1. The telephone wiring 5 is split into distinct segments 5a, 5b, and 5c. Low-Pass Filters (LPF) and High-Pass Filters (HPF) are coupled to each wire segment end, in order to split between the telephony and the data signals. As shown in FIG. 6, LPF's 21b and 21c are respectively attached to opposite ends of the wiring segment 5b. The LPF's are designed to allow passing of the telephony signals, and are connected together thus offering a continuous path for the telephony signals. Access to the telephony signals is made via connectors 12a and 12b in the outlets, into which telephone devices 13a and 13b are connected via connectors 14a and 14b respectively. Thus, the telephony service is fully retained. The data signals, carried in the high part of the spectrum, are accessed via HPF's 22b and 22c, also coupled respectively to opposite ends of the telephone wire segment 5b. HPF's 22a and 22d are connected to the ends of the wire segments 5a and 5c respectively. Each HPF is connected to a modem 23, which transmits and receives data signals over the telephone wiring. Modems 23a, 23b, 23c, and 23d are connected to HPF's 22a, 22b, 22c and 22d respectively. Data units 24a and 24b are connected to the outlets 31a and 31b respectively, via a respective connector (not shown in the Figure) in each outlet. The data units are coupled via a respective DTE interface in the outlet. Outlets 31a and 31b comprise DTE interfaces 29a and 29b respectively. The three data streams in each outlet, two from each modem and one from the DTE, are handled by an adapter 28a and an adapter 28b, which serve outlets 31a and 31b, respectively. While FIG. 6 describes an embodiment wherein all the components for the relevant functions are housed within the outlet, other embodiments are also possible, wherein only some of the components for these functions are contained within the outlet.
Life-Line
The term “life-line” as used herein denotes the basic use of the telephone service for emergency purposes. As such, it is required that a malfunction of any other system or service (e.g. electricity) will not degrade the telephone system capability. In practical terms, this means that as long as an operational telephone set is connected to the exchange via continuous two wires, the telephone service will be maintained, even in the case of power outage.
There is thus a widely recognized need for, and it would be highly advantageous to have, a means for implementing a telephone system in-home, wherein the telephone units can be networked within the home as well as to multiple external subscriber lines, without requiring the installation of additional wires within the home. This goal is met by the present invention.